A new cross-bridge model has been developed based on the concept that the binding of ATP to the myosin-bridge-actin complex not only weakens the binding of actin to myosin but also increases the preferred angle of the attached cross-bridge from 45 degrees to 90 degrees. This concept is combined with the biochemical concept of rapid equilibria between attached and detached states and the physiological concept of an elastic cross-bridge to allow a model in which myosin does not have to dissociate from actin each time an ATP molecule is hydrolyzed. However, when the muscle is moving detachment of the cross-bridge does occur with no loss of free energy. This new model is therefore consistent with recent biochemical evidence suggesting that ATP hydrolysis can occur without mandatory dissociation of the actomyosin complex.